The present invention relates generally to devices and methods for extracorporeal treatment of body fluids, such as extracorporeal treatment of blood, to remove toxins and restore physiological balance. The invention also relates in other aspects to devices and methods for performing peritoneal dialysis.
Extracorporeal blood treatment has been used to remove toxins in several therapeutic settings including drug overdose, autoimmune diseases, kidney insufficiency or failure, and liver insufficiency or failure. The treatment can include withdrawing blood from the patient and passing the blood through a purification system. Examples of such systems include hemodialysis, hemofiltration, hemoperfusion, and plasmapheresis systems.
Some blood treatment therapies rely on the efficacy of sorbents. One example of a system that uses sorbents is the BioLogic-DT System (“the DT System”). The DT System includes a flat plate dialyzer that has a semi-permeable membrane. A sorbent suspension containing powdered charcoal and various ion exchangers is passed in contact with the dialysate side of the dialyzer membrane, and blood is passed in contact with the opposite side of the membrane. The sorbents can also be pre-equilibrated with a variety of additional or replacement nutrients and beneficial components that can cross the membrane to the blood stream. A portion of blood, including toxins and other blood components such as nutrients and electrolytes, can be transported across the membrane by diffusion and convection. Sorbents come into contact with and bind certain of these components in the dialysate. Toxins can be bound by the sorbents, while many nutrients and electrolytes are not bound. The non-bound components are transported back across the membrane to the blood side. Blood treated in the dialyzer then returns to the patient. The DT System uses alternating vacuum and pressure in the dialysate to move the dialyzer membranes, thus changing the volume of the blood-side circuit. This, in combination with control of valves in the blood side circuit, results in the unidirectional flow of blood through the blood-side circuit. The membrane motion also actively mixes the sorbent suspension at the membrane surface, reducing stagnation, and chemical saturation of the sorbents by toxins at the membrane surface. Sorbent suspension also circulates between a reservoir and the dialyzer.
Another approach is the use of a sorbent suspension to treat blood components extracted from whole blood via plasma filtration. One example of this approach is the BioLogic-PF System (“the PF System”). In the PF System, blood is perfused through a hollow-fiber plasmafilter, and the transmembrane pressure is alternated from positive to negative on a regular cycle. In each cycle, about 40 ml of filtrate (plasma) is drawn out of the blood through the membranes, treated, and then returned to the blood, about 5 times per minute. Outside the membranes is a sorbent suspension containing charcoal or other powdered sorbent. The sorbent is also circulated between a reservoir and the case surrounding the hollow fiber membranes. Contact of the filtrate with the sorbent suspension removes soluble and protein-bound toxins from the filtrate. The filtrate then returns to the blood depleted of these toxins. Similar to the DT System, the sorbent has low capacity and affinity for many nutrients and can even supply nutrients by desorption. The back and forth motion of the filtrate reduces stagnation and chemical saturation of the sorbents on the outside of the plasma filter membranes and also avoids excessive red cell polarization on the blood side of the membranes.
Sorbents used in the DT and PF Systems have adequate capacity to remove toxins from blood and to restore a physiological balance; however, the presence of sorbent particles adjacent to dialysis or plasma filtration membranes gives rise to significant technical challenges, and often leads to mechanical obstructions. As a result, the use of a sorbent suspension adjacent to a separation membrane imposes severe limitations upon membrane choices and treatment system design. Furthermore, supplies of dialysis membranes suitable for such use in the DT System are limited, and it is expected that in the near future such membranes will not be commercially available. Recent advances in membrane technology have provided a variety of new membranes, such as, for example, highly efficient hollow fiber membranes; however, the challenges of passing a sorbent suspension in contact with such membranes have been a limiting factor in the overall success achieved in the use of a sorbent suspension in systems including such membranes.
In light of the above, there is a continuing need for improved systems for the treatment of body fluids in patients suffering from diseases and conditions such as drug overdose, autoimmune diseases, kidney insufficiency or failure, and liver insufficiency or failure. In particular, there is a need for systems that take advantage of new membrane technology, while also having the advantages provided by the use of sorbent suspensions. The present invention addresses these needs and provides additional benefits.